THE MUSCCLAB SYSTEM 199
and the insertions of the sernimeinbranosus and semi-tendinosus move upwards as the child learns to walk and stand. The fascial attachment is feeble in the Gorilla. The fiehiimemlranosiis runs to the tibia over an area situated more proximal than those ui the other hamstrings. Its insertion was studied :ii detail by G-ratiolet «330».
The tibialis antieus is built on the same plan in all the Apes. In the Chimpanzee it arises from the external condyle and upper half of the outer surface of the shaft of the tibia, the interosseous membrane and the fascia over it and between it and the extensor iongus digitoruin. It splits into two bellies which end in long tendons (fig. 86, ii). The tendons are inserted into the internal cuneiform bone and the base of the tirst rneta-tarsal. This double insertion is associated wiih the use of the hallux as a thumb : and Hepburn \83» believes the two divisions correspond to the extensor ossis metacarpi and extensor prirni internodii pollicis.
The extensor Iongus digitomm arises from the external condyle of the tibia, the anterior border of the head of the fibula, the antero-mesial aspect of the shaft of the fibula, the fascia over it and the septa dividing it from the neighbouring muscles. It passes under the annular ligament and ends in tendons for the four outer toes. The tendons show many individual peculiarities in the manner in which they communicate with one another on the dorsum of the foot. The tendons form expansions over the metacarpo-phalangeal and interphalangeal joints. They are joined by the lumbricales, interossei and extensor brevis digitoruin.
The extensor Iongus hallncis, which may corre-